Discharging a firearm causes gases to be produced through rapid, confined burning of a propellant that accelerates a projectile. This typically generates a loud noise, a muzzle flash of light, and sometimes visible gas discharge. Often, it is desirable to reduce the amount of noise and light produced by discharging a firearm. For example, military snipers or special operations forces personnel may require stealth to successfully complete missions. Suppressors, or silencers, are typically connected to the muzzle end of a firearm to temporarily capture gas that exits the muzzle. Some suppressor designs divert a portion of the discharge gas to a secondary chamber, such that the gas does not exit the suppressor by the same path as the projectile. The gas is released from the suppressor at a significantly reduced pressure. In general, the more gas a suppressor captures or redirects, the quieter the discharge sound of the firearm. Flash hiders operate in much the same way upon discharge of the firearm, dispersing ignited media thereby diffusing flash.
The presence of a suppressor and/or flash hider, however, may increase the back pressure of the gas in the barrel of the firearm. Increased back pressure in the barrel can influence the firearm's operation. For example, some firearms are gas-operated and use discharge gas pressure in the barrel to reload the firearm. Thus, increasing gas back pressure in the barrel can increase forces acting on the reloading components and affect their operation. Higher forces can also reduce the service life of the reloading components. For at least these reasons, accurately and predictably controlling the pressure attributes of firearm suppressors and flash hiders remains an active field of endeavor.